Palladium Element: Information, Properties, and Applications

Palladium element properties
Palladium is a metallic element resembling platinum in appearance. It doesn't tarnish when exposed to air, and thus, is used widely in jewelry making. This Buzzle post sheds light on the facts, properties, and applications of palladium.
Who Discovered Palladium?
William Hyde Wollaston discovered the metallic element palladium in the year 1803. This element is considered to be one of the rarest elements found in the Earth's crust.
Palladium, pronounced as 'puh-LAY-dee-um', is an element having steel-white color and a silvery-white luster. It is a transition metal, and is known to occur in some nickel and copper ores. It occurs as a solid, and becomes malleable as well as ductile when tempered by applying heat. Subjecting this metal to heat makes it soft. On the other hand, working on this metal when it is cold enhances its strength.

It has a paramagnetic ordering. It belongs to a group 'PGM', which is called the platinum group of metals. The other elements belonging to this family are ruthenium, rhodium, osmium, iridium, and platinum. Palladium is known to be denser and has a lower melting point as compared to the other elements of this group.
Palladium Element Facts
Palladium bar
✦ The chemical symbol of this element is Pd.
✦ It belongs to the group 10 and block d of the periodic table.
✦ Palladium contains seven isotopes, out of which six are in their stable state.
✦ It is named after Pallas, which was the second asteroid to be discovered. The word Pallas (in Greek mythology) represents the Goddess of Wisdom and Warfare.
✦ A chloride compound of this element was used to treat tuberculosis in earlier times. However, it was discontinued due to its adverse side effects on the human body.
✦ The CAS registry ID of this element is 7440-05-3.
✦ Palladium is chiefly produced by four countries, namely Russia, Canada, US, and South Africa.
Properties of Palladium
Physical Properties
✦ The density of palladium at room temperature is 12023 kg/m3. Whereas, its density at its melting point is 10.38 g/cm3.
✦ Its boiling point is 2963°C, or 3236.15 K.
✦ Palladium is over 70% reflective.
✦ The melting point of this element is 1554.9°C, or 1828.05 K.
✦ The value of thermal conductivity is 72 W/m/K.
✦ Its Young's, bulk, and rigidity modulus is equal to 121 GPa, 180 GPa, and 44 GPa, respectively.
✦ Palladium in a powdered form is considered to be pyrophoric. That is, it emits sparks when rubbed with steel.
✦ The speed of sound from a thin palladium rod at about 20ºC is 3070 m/s.
✦ Its Poisson's ratio is 0.39.
✦ The value of electronegativity on Pauling's scale is 2.20 Pauling units.
✦ The values of brinell, vickers, and moh's mineral hardness are 37.3 MN/m2, 461 MN/m2, and 4.75 respectively.
✦ The coefficient of thermal expansion is 11.8 × 10-6 K-1.
✦ Its electrical resistivity is 10.8 × 10-8 Ω m.
✦ The values of first, second, and third ionization energies are 804.4 kJ/mol, 1870 kJ/mol, and 3177 kJ/mol, respectively.
Chemical Properties
✦ The atomic number of palladium is 46, and its atomic mass is 106.42.
✦ Its electron distribution in the shells can be represented as 2, 8, 18, 18, 0.
✦ The electronic configuration of this element (in terms of a noble element) is represented as [Kr] 4d10.
✦ This metal acts as a sponge, and has the tendency to absorb hydrogen multiple times its original volume.
✦ The molar volume of this metal is 8.56 cm3/mol.
✦ It doesn't react with acids at room temperature. However, hot concentrated acids such as nitric and sulfuric acid can react with this element.
Palladium Shell Diagram
Palladium shell diagram
Shell diagrams are used for the representation of the placement of electrons in the atoms. The diagram above represents the shell structure of palladium atoms. They consist of 2, 8, 18, 18 electrons in their 1st, 2nd, 3rd, and 4th shell, respectively.
Palladium Orbital Diagram
Palladium orbital diagram
Orbital diagrams are used for the representation of electrons in sub-orbitals of atoms. The diagram above represents the orbital structure of palladium atoms. All the shells of these atoms from 1s to 4d are completely filled.
Applications of Palladium
✦ Dehydrogenation and hydrogenation reactions sometimes use palladium (in the powdered form) as an accelerator.
✦ Palladium is used in making jewelry and ornaments. It can be considered as a strong substitute for gold and platinum.
✦ It is used for making coins as well as astronomical mirrors.
✦ It is used in dental applications for making caps, bridges, and crowns.
✦ This metal is used as an alloying agent. It is mixed with platinum to make a strong alloy.
✦ It is used in its radioactive form for treating cancer.
✦ Palladium is used in plating electronic devices, as well as photograph printing.
✦ This element is used as a catalyst in the process of polyester production.
✦ It can also be used to filter harmful substances from groundwater.
The reactivity a of metal defines its scope of usage. Palladium remains unaffected at ordinary temperatures. This property makes it a very efficient metal.